Central-European severe weather outbreak August 15th

Many countries were affected in a belt extending from northern Italy to the Baltic Countries. Sadly enough, 8 people lost their lives due to the severe weather, most of them due to falling objects in strong wind gusts, 3 in Poland, 2 in Slovakia, 2 in Italy and 1 victim in Austria. ESTOFEX noticed the seriousness of situation a few days beforehand and an extended forecast was issued on August 13th. The next day it became obvious that the highest threat level, 3, would be necessary for some regions and a convective forecast was posted.

The first storms started quite early, before noon, and in very strong wind fields. They quickly organised into supercells. One of the supercells hit the city of Katowice, accompanied by damaging hailstorm. A video of the falling hail can be found here. But Poland was not the only region, where explosive thunderstorm formation occurred. Northern Italy and Slovenia followed very soon. In very a unstable environment, the storms produced swaths of large hail, some of the hailstones had a diameter of more than 5 cm. Later in the day, the situation became even more serious as a line of supercells developed over southern Poland and moved to the NE. A forecast update was issued approximately soon afterwards. These storms produced at least 8 tornadoes. Here are a few photo's:


Source: AP


Source: Agencja Gazeta

One of them has been rated F3, i.e. a strong tornado, and caused considerable damage to houses and vegetation. Tornadoes were extensively documented by local storm chasers and some videos can be found here. A very dramatic video comes from the inside of a bus, that was overturned by severe tornadic winds. Meanwhile, a line of HP supercells organized into a powerful bow echo over Slovenia and headed to the north. Extensive wind and hail damage occurred with this system across Slovenia, W. Hungary, E.Austria and SW. Slovakia. In Austria and Slovakia, hailstones of 5 cm diameter were found after the storm and roofs of some houses were completely destroyed. What is more, mountainous regions of Middle Europe experienced flash flooding as storms repeatedly moved over the same places.

Violent tornado in northern France

A violent tornado has struck the communities of Hautmont and Maubeuge in northern France on August 3rd at around 20:30 UTC. Severe weather experts of the Belgian Meteorological Institute Karim Hamid and Karel Holvoet have conducted a damage survey and rate the damage F4 on the Fujita scale, with wind speeds likely exceeding 300 km/h or 90 m/s. Their report (in Dutch) can be found here. Pierre Mahieu and Emmanuel Wesolek of Keraunos have published this case study in French. The severity of the damage is also clear from images that have appeared in the press, for example the following...

photo: AFP / P. Frutie

...and from these photos. The tornado sadly caused 3 fatalities and left 18 people injured. Moreover, more than 700 homes were damaged, among which a few dozens have become inhabitable. A television crew of LC1 has flown over the affected areas resulting in the following TV report.
ESTOFEX had initially issued a level 1 for this area. It appeared that strong low-level wind shear and high storm-relative helicity would enable rotating updrafts to form with a chance of tornadoes. However, low amounts of instability forecast by the numerical model precluded the issuance of a higher risk category until the mid-evening. At 20:12, shortly before the deadly tornado struck, a forecast update was issued because it appeared that strong convective storms were ongoing in an environment much more unstable than expected earlier in the day. This is one of the strongest, if not the strongest tornado that occurred since the start of the European Storm Forecast Experiment.